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Could Sugar Be a Dangerous Toxin?

That high sugar consumption contributes to weight gain has widely become accepted as a fact, but the possibility that eating the sweet stuff could make us actually sick is another matter. Questions about potentially devastating health effects of sugar are the subject of a recent article by Gary Taubes in The New York Times Magazine (4/17/2011).

While Taube’s investigation stops short of passing final judgment, he does in fact make a persuasive argument that sugar may be a dangerous toxin or poison on par with tobacco and alcohol – “something that’s killing us.”

The latter are not Taube’s words but those of Robert Lustig, a specialist on pediatric hormone disorders and a renowned expert in childhood obesity at the School of Medicine of the University of California in San Francisco. Lustig has long been convinced that sugar is not only bad for our health because it offers too many empty calories without much nutritional value. “It’s not about the calories,” he insists. “It’s a poison.”

By sugar, he does not single out the white granulated variety that you pour in your tea or coffee or on top of your breakfast cereal, which is known as sucrose. He also (and especially) includes high-fructose corn syrup (HFCS), which is almost omnipresent in processed foods and soda drinks. In fact, over the last 30 years, HFCS has become the sweetener of choice for manufacturers of processed foods and sodas, primarily because it’s cheaper than refined sugar. Only now the tide seems to be turning back in favor of old-fashioned sugar, as HFCS is becoming increasingly unpopular with health-conscious consumers.

Lustig agrees with the assessment of the majority of nutrition experts that the high sugar content in the typical American diet plays a major role in the current obesity- and diabetes epidemic, but he goes much further than many of his colleagues. He believes that sugar is also a likely dietary cause of several other chronic ailments and diseases of Western lifestyles – like heart disease, hypertension and some types of cancer. Consequently, he demands that sugar should be classified as a toxic substance.

From the start, Taubes does not hide his belief that the professor has a point: “ Lustig, who has genuine expertise, has accumulated and synthesized a mass of evidence… compelling enough to convict sugar,” he writes.

Lustig’s general (some say “loose”) use of the term “sugar” has made him vulnerable to his critics. By “sugar,” he says, he means both sucrose (e.g. beet- and cane sugar) as well as HFCS. Sucrose consists of carbohydrate glucose and carbohydrate fructose as a 50-50 mixture. By contrast, HFCS contains 55 percent fructose and 45 percent glucose. Since fructose tastes much sweeter than glucose, the desired sweetening effect is higher in HFCS than in refined sugar. Still, both forms of sugar end up as a glucose-fructose combination in our bodies, or as Taubes puts it: “The question, then, isn’t whether high-fructose corn syrup is worse than sugar; it’s what do they do to us.”

That is also Lustig’s argument. It’s not about what kind of sugar we should use and what kind we should avoid. It’s not even about the empty calories many of our food products are overloaded with. Rather, it is about the “unique characteristics” of sugar and the ways our bodies metabolize the fructose in it “that may make it singularly harmful, at least if consumed in sufficient quantities.”

And this is where Lustig makes his case most compelling: The fructose component of both sugar and HFCS is primarily metabolized by the liver, while glucose is metabolized by every cell in the body. The more fructose you consume, the harder the liver has to work. And if you take high amounts of fructose in liquid form, e.g. through sodas and fruit juices, the liver will have to struggle even more to handle the onslaught. Eventually, the poor organ won’t be able to keep up metabolizing and will eventually convert much of the fructose to fat. This also can induce a condition known as insulin resistance, which is well known as a causal factor of type 2 diabetes.

A growing number of physicians and medical authorities now agree that high sugar consumption is harmful in a number of ways. For instance, “metabolic syndrome,” which includes significant risk factors for heart disease and diabetes, is dramatically on the rise. The Centers for Disease Control and Prevention (CDC) estimates that currently 75 million Americans suffer from metabolic syndrome.

Insulin resistance and metabolic syndrome in connection with high fructose intake have been studied in clinical laboratories for some time. When test animals are given lots of sugar, their livers eventually turn “fatty.” As one scientist involved in such studies put it: “If you want to cause insulin resistance in laboratory rats, feeding them diets that are mostly fructose is an easy way to do it.”

Chronically elevated insulin often leads to unhealthy increases in cholesterol as well. Higher triglyceride levels can lower HDL (“good”) cholesterol, further worsening insulin resistance and also the risk of heart disease.

Taubes waits almost until the end of his article to make his own, perhaps most devastating argument against sugar. “What are the chances,” he asks, “that sugar is actually worse than Lustig says it is?”

One of the diseases that routinely coincide with obesity, diabetes and metabolic syndrome is – cancer. The World Health Organization (WHO) through its International Agency for Research on Cancer concluded after a large population study in 2004 that there are clearly identifiable connections between these various diseases. “You are more likely to get cancer if you are obese or diabetic than if you’re not, and you are more likely to get cancer if you have metabolic syndrome than if you don’t.”

Does this mean that a large percentage of cancers may be caused by our dietary and lifestyle choices? The World Cancer Research Fund and the American Institute for Cancer Research seem to back up such thinking. But how so?

Taubes cites clinical research that has connected insulin resistance to the growth of tumors. “Some cancers develop mutations that serve the purpose of increasing the influence of insulin on the cell; others take advantage of the elevated insulin levels that are common to metabolic syndrome, obesity and type 2 diabetes. Some do both.” Researchers believe that many precancerous cells would not mutate into malignant ones “if they weren’t being driven by insulin to take up more and more blood sugar and metabolize it.”

In other words, while we still may not know enough about the dietary causes of cancers, there are strong indications that insulin resistance caused by high sugar intake plays a role in the formation of at least some types of cancer – and that should be enough to set off the alarm bells.

Taubes himself is reluctant to do just that, and so the article ends not with a call to arms but rather with a shrug. “Officially,” he writes, “I’m not supposed to worry because the evidence isn’t conclusive, but I do.” – Me too…

To read the article, “Is Sugar Toxic?” by Gary Taubes, go to www.nytimes.com

Timi Gustafson R.D. is a clinical dietitian and author of “The Healthy Diner – How to Eat Right and Still Have Fun™,” is available on her blog http://www.timigustafson.com and at Amazon. Her latest book, “Kids Love Healthy Foods™” is now available in e-book format at www.amazon.com

Note: This is a seattlepi.com reader blog. It is not written or edited by the P-I. The authors are solely responsible for content. E-mail us at newmedia@seattlepi.com if you consider a post inappropriate.